Presently, the method for growing a nano-carbon material includes three types: one is an arc-discharge method, another is a material mixed by metal and graphite, which are vaporized via laser vaporization, and the other is a CCVD (Catalytic Chemical Vapor Deposition) method.
The arc-discharge method is described as follows introducing helium into a stainless steel reactor which maintains the pressure at 500 Torr, connecting a DC power to the two graphite electrodes in the reactor to provide a voltage at 20 V, and forming arcs when two electrodes are close enough, and the produced current is about 150 A. After a period of time, there finds some materials containing carbon deposited on the cathode and also the reactor. Those deposited on the cathode are the mixture of nano-carbon material, carbon granules, fullerences, and a large amount of amphorous carbons. The advantages of the arc-charge method include the simple apparatus, and the fast speed for producing the nano-carbon material. But the disadvantage of the arc-charge method is a large amount of impurities are mixed therein. The complicated purification processes must be executed to purify thereof, and it is an improper method for producing the nano-carbon material with high purity.
The laser vaporization employs a high power laser to shoot the target, which is made of catalytic metal and carbon, and then vaporizes it. Continuously, an inert gas (e.g., helium or neon) is introduced to bring thereof into the high temperature reactor to form the nano-carbon material on the substrate which is located at the exit having a lower temperature of the reactor. The advantage of this method is that the purity of the nano-carbon material can be achieved up to 90%. But the disadvantage of the laser vaporization is a very low production rate and thus is unsuitable for mass production.
The CCYD (Catalytic Chemical Vapor Deposition) method is trying to introduce the hydrocarbon (mostly are CH4, C2H2, C2H4, and C6H6, and generally also mixed with hydrogen) or the carbon monoxide into a one- or multi-stages high temperature reactor to produce the thermal pyrolysising on some catalytic metals. The products might be a nano-carbon material, an amphorous carbon, or a full carbon fiber. The advantage of this method is that an orientated nano-carbon material can be grown via the pretreatment of the substrate and the catalytic metal to benefit the fabrication of the element. The disadvantage of this method is that the adhesion between the substrate and the nano-carbon material is bad. Generally, the temperature raising speed of a high temperature reactor is slow and the temperature climbing status of large surfaces is uneven, thus maximizing the reaction area of the process and achieving a mass production all will be limited by the conditions of the high temperature reactor.
Besides, the methods described above all are high temperature processes (700˜1200° C.). Because of the high temperature of these methods, they cannot be matched to the silicon semiconductor manufacturing process which is already commercialized.
Besides, the methods described above all are high temperature processes (700˜1200° C.). Because of the high temperature of these methods, they cannot be matched to the silicon semiconductor manufacturing process which is already commercialized.
Because of the technical defects described above, the applicant keeps on carving unflaggingly to develop “thermal pyrolysising chemical vapor deposition method for synthesizing nano-carbon material” through wholehearted experience and research.